FAILED: patch "[PATCH] tracing: Do not stop recording comms if the trace file is" failed to apply to 4.9-stable tree - Linux-stable-mirror

21 Jun 2021

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
...
From 4fdd595e4f9a1ff6d93ec702eaecae451cfc6591 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" rostedt@goodmis.org
Date: Thu, 17 Jun 2021 14:32:34 -0400
Subject: [PATCH] tracing: Do not stop recording comms if the trace file is
 being read
A while ago, when the "trace" file was opened, tracing was stopped, and
code was added to stop recording the comms to saved_cmdlines, for mapping
of the pids to the task name.
Code has been added that only records the comm if a trace event occurred,
and there's no reason to not trace it if the trace file is opened.
Cc: stable@vger.kernel.org
Fixes: 7ffbd48d5cab2 ("tracing: Cache comms only after an event occurred")
Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e220b37e29c6..d23a09d3eb37 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2198,9 +2198,6 @@ struct saved_cmdlines_buffer {
 };
 static struct saved_cmdlines_buffer *savedcmd;
-/* temporary disable recording */
-static atomic_t trace_record_taskinfo_disabled __read_mostly;
-
 static inline char *get_saved_cmdlines(int idx)
 {
    return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
@@ -3996,9 +3993,6 @@ static void *s_start(struct seq_file *m, loff_t *pos)
    	return ERR_PTR(-EBUSY);
 #endif
-	if (!iter->snapshot)
-		atomic_inc(&trace_record_taskinfo_disabled);
-
    if (*pos != iter->pos) {
    	iter->ent = NULL;
    	iter->cpu = 0;
@@ -4041,9 +4035,6 @@ static void s_stop(struct seq_file *m, void *p)
    	return;
 #endif
-	if (!iter->snapshot)
-		atomic_dec(&trace_record_taskinfo_disabled);
-
    trace_access_unlock(iter->cpu_file);
    trace_event_read_unlock();
 }

    